help - Boiler and hot water issues Worcester 28CDI

Recently moved into a house electricity was turned off and for the first day and half boiler was locking out everytime hot water was run, and ended up running cold.

Followed instructions to increase boiler pressure from just under 1 to 1.5 bar when heating turned on and go up to 2 bar. And hot water seemed to run in kitchen fine. However upstairs sink only running cold water. (bath upstairs running hot water fine).

Previous owner indicated that water was having to run with more pressure before the boiler kicked in than normal and upped the pressure of the boiler to 2 bar. Now when heating goes on the pressure gauge is heading up above 3.5 bar and still no hot water in upstairs tap in the sink.

Any suggestions as now saying this was not logged as an issue within the given 5 days, where are I thought this is all linked hot water and heating issues were logged on day one as every time tried to run hot water the boiler system locked out. and at no point offered a professional to come out and attend the issues. Any thoughts on where issue lies next steps? Thanks

To fix this one properly you will need an engineer on site to diagnose the problems. You should certainly not have to put any more than 1.5 bar into the boiler, any more and you risk over-presurising it.
You may have issues with the basin tap rather than the boiler as it may not be passing enough water to activate the flow switch in the boiler.
There could be a hundred an one other issues so get a gas safe in to give it the once over.